1. Field of the Invention
The present invention relates to drive units and electric-motor-assisted bicycles, and more particularly to a drive unit attached to a vehicle-body frame included in an electric-motor-assisted bicycle and an electric-motor-assisted bicycle including such a drive unit.
2. Description of the Related Art
Bicycles are used by many people, regardless of age and gender, as a handy transportation means. In recent years, electric-motor-assisted bicycles that add driving forces from the motor to pedaling forces from the rider to assist the rider have become popular. Such an electric-motor-assisted bicycle is disclosed in JP 2014-196080 A, for example.
JP 2014-196080 A describes an electric-motor-assisted bicycle that includes a drive unit. The drive unit includes a housing and a crank axle. The crank axle extends through the housing in the left-to-right direction with respect to the vehicle. Pedals are mounted on the crank axle via arms. The drive unit is attached to the bottom of the vehicle-body frame.
The drive unit further includes a motor and a substrate. The motor is housed in the housing and generates drive forces to be added to the tread force of the rider to assist the rider. The substrate is housed in the housing and controls the electric power supply to the motor.